The invention relates to a compression roller for paper producing machinery intended to deliver a linear pressure to a second cooperating roller. The compression roller includes a rotatable tubular outer casing whose cross section is circular and also includes a nonrotatable roller core. The core includes a cylinder and a rod-like piston, extending over the entire length of the roller, which is radially adjustable. Pivotally adjusted to this piston and urged thereby against the inside of the casing is a support bar which extends substantially over the length of the roller and has an external contour which substantially conforms to the shape of the roller casing.
If the compression rollers were to be employed in normal use without further precaution, they would be bent out of shape and thus would entail faulty treatment of the paper web.
For this reason, there has been developed the so-called floating roller, in which a support bar is pushed against the roller casing from the inside and where a pressure medium is placed between the casing and the support bar so that the casing floats on a hydraulic carrier film. This carrier film is built up by forming a wedge-shaped space at the outside surfaces of the carrier rail, as disclosed in German Offenlegungsschrift 1 461 066.
A disadvantage of this known apparatus is that the hydrodynamic carrier film depends on the rotational speed. When the roller is standing still, the carrier rail and the casing are in metallic contact so that when the machinery is started up, the casing is easily damaged. Furthermore, the direction of rotation is significant in the formation of the film.